HR: 1330h
AN: PP12A-0226    [PDF]
TI: A review of palaeoproductivity records from the N Pacific: The end of the iron hypothesis?
AU: * Kienast, S S
EM: skienast@whoi.edu
AF: Dept. Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 United States
AU: Hendy, I L
EM: ihendy@umich.edu
AF: Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109 United States
AU: Crusius, J
EM: jcrusius@usgs.gov
AF: U.S. Geological Survey, Woods Hole, Woods Hole, MA 02543 United States
AU: Pedersen, T F
EM: tfp@uvic.ca
AF: School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8P 5C2 Canada
AU: Calvert, S E
EM: calvert@eos.ubc.ca
AF: Dept. Earth and Ocean Sciences, University of British Columbia, Vancouver, BC V6T 1Z4 Canada
AB: Today, the subarctic North Pacific is a high nitrate-low chlorophyll (HNLC) region, where phytoplankton growth rates, especially those of diatoms, are enhanced when iron is added. Accordingly, it has been suggested that glacial Fe-laden dust might have increased primary production in this region. Here we review published palaeoceanographic records of export production over the last 800 kyrs from the open North Pacific (north of 35\deg N). We find different patterns of export production change over time in the various domains of the North Pacific (NW and NE subarctic gyres, the marginal seas and the transition zone). However, there is no compelling evidence for an overall increase in productivity during glacials in the HNLC region. Potential reasons for the lack of increased glacial export production include the possibility that Fe-fertilization rapidly drives the ecosystem towards limitation by another nutrient. This effect would have been exacerbated by an even more stable mixed layer compared to today. Previous studies from the Southern Ocean HNLC region have similarly concluded that there is no compelling evidence for a glacial increase in export production in the Antarctic zone of the the Southern Ocean. Taken together, these observations challenge the paradigm that dust-born Fe fertilization of HNLC regions during dustier glacial times has contributed to the glacial draw down of atmospheric CO$_{2}$.
DE: 4267 Paleoceanography
DE: 4805 Biogeochemical cycles (1615)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting